root / prex-0.9.0 / usr / server / fs / vfs / vfs_bio.c @ 03e9c04a
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1 | 03e9c04a | Brad Neuman | /*
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2 | * Copyright (c) 2005-2007, Kohsuke Ohtani
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3 | * All rights reserved.
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4 | *
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5 | * Redistribution and use in source and binary forms, with or without
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6 | * modification, are permitted provided that the following conditions
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7 | * are met:
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8 | * 1. Redistributions of source code must retain the above copyright
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9 | * notice, this list of conditions and the following disclaimer.
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10 | * 2. Redistributions in binary form must reproduce the above copyright
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11 | * notice, this list of conditions and the following disclaimer in the
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12 | * documentation and/or other materials provided with the distribution.
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13 | * 3. Neither the name of the author nor the names of any co-contributors
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14 | * may be used to endorse or promote products derived from this software
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15 | * without specific prior written permission.
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16 | *
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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18 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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21 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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22 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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23 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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24 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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25 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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26 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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27 | * SUCH DAMAGE.
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28 | */
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29 | |||
30 | /*
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31 | * vfs_bio.c - buffered I/O operations
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32 | */
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33 | |||
34 | /*
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35 | * References:
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36 | * Bach: The Design of the UNIX Operating System (Prentice Hall, 1986)
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37 | */
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38 | |||
39 | #include <sys/prex.h> |
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40 | #include <sys/list.h> |
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41 | #include <sys/param.h> |
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42 | #include <sys/buf.h> |
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43 | |||
44 | #include <limits.h> |
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45 | #include <unistd.h> |
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46 | #include <stdlib.h> |
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47 | #include <string.h> |
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48 | |||
49 | #include "vfs.h" |
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50 | |||
51 | /* number of buffer cache */
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52 | #define NBUFS CONFIG_BUF_CACHE
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53 | |||
54 | /* macros to clear/set/test flags. */
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55 | #define SET(t, f) (t) |= (f)
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56 | #define CLR(t, f) (t) &= ~(f)
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57 | #define ISSET(t, f) ((t) & (f))
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58 | |||
59 | /*
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60 | * Global lock to access all buffer headers and lists.
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61 | */
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62 | #if CONFIG_FS_THREADS > 1 |
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63 | static mutex_t bio_lock = MUTEX_INITIALIZER;
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64 | #define BIO_LOCK() mutex_lock(&bio_lock)
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65 | #define BIO_UNLOCK() mutex_unlock(&bio_lock)
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66 | #else
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67 | #define BIO_LOCK()
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68 | #define BIO_UNLOCK()
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69 | #endif
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70 | |||
71 | |||
72 | /* set of buffers */
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73 | static char buffers[NBUFS][BSIZE]; |
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74 | |||
75 | static struct buf buf_table[NBUFS]; |
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76 | static struct list free_list = LIST_INIT(free_list); |
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77 | |||
78 | static sem_t free_sem;
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79 | |||
80 | |||
81 | /*
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82 | * Insert buffer to the head of free list
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83 | */
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84 | static void |
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85 | bio_insert_head(struct buf *bp)
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86 | { |
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87 | |||
88 | list_insert(&free_list, &bp->b_link); |
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89 | sem_post(&free_sem); |
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90 | } |
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91 | |||
92 | /*
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93 | * Insert buffer to the tail of free list
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94 | */
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95 | static void |
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96 | bio_insert_tail(struct buf *bp)
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97 | { |
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98 | |||
99 | list_insert(list_prev(&free_list), &bp->b_link); |
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100 | sem_post(&free_sem); |
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101 | } |
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102 | |||
103 | /*
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104 | * Remove buffer from free list
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105 | */
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106 | static void |
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107 | bio_remove(struct buf *bp)
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108 | { |
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109 | |||
110 | sem_wait(&free_sem, 0);
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111 | ASSERT(!list_empty(&free_list)); |
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112 | list_remove(&bp->b_link); |
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113 | } |
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114 | |||
115 | /*
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116 | * Remove buffer from the head of free list
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117 | */
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118 | static struct buf * |
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119 | bio_remove_head(void)
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120 | { |
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121 | struct buf *bp;
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122 | |||
123 | sem_wait(&free_sem, 0);
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124 | ASSERT(!list_empty(&free_list)); |
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125 | bp = list_entry(list_first(&free_list), struct buf, b_link);
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126 | list_remove(&bp->b_link); |
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127 | return bp;
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128 | } |
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129 | |||
130 | /*
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131 | * Determine if a block is in the cache.
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132 | */
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133 | static struct buf * |
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134 | incore(dev_t dev, int blkno)
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135 | { |
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136 | struct buf *bp;
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137 | int i;
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138 | |||
139 | for (i = 0; i < NBUFS; i++) { |
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140 | bp = &buf_table[i]; |
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141 | if (bp->b_blkno == blkno && bp->b_dev == dev &&
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142 | !ISSET(bp->b_flags, B_INVAL)) |
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143 | return bp;
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144 | } |
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145 | return NULL; |
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146 | } |
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147 | |||
148 | /*
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149 | * Assign a buffer for the given block.
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150 | *
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151 | * The block is selected from the buffer list with LRU
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152 | * algorithm. If the appropriate block already exists in the
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153 | * block list, return it. Otherwise, the least recently used
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154 | * block is used.
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155 | */
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156 | struct buf *
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157 | getblk(dev_t dev, int blkno)
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158 | { |
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159 | struct buf *bp;
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160 | |||
161 | DPRINTF(VFSDB_BIO, ("getblk: dev=%x blkno=%d\n", dev, blkno));
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162 | start:
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163 | BIO_LOCK(); |
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164 | bp = incore(dev, blkno); |
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165 | if (bp != NULL) { |
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166 | /* Block found in cache. */
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167 | if (ISSET(bp->b_flags, B_BUSY)) {
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168 | /*
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169 | * Wait buffer ready.
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170 | */
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171 | BIO_UNLOCK(); |
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172 | mutex_lock(&bp->b_lock); |
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173 | mutex_unlock(&bp->b_lock); |
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174 | /* Scan again if it's busy */
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175 | goto start;
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176 | } |
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177 | bio_remove(bp); |
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178 | SET(bp->b_flags, B_BUSY); |
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179 | } else {
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180 | bp = bio_remove_head(); |
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181 | if (ISSET(bp->b_flags, B_DELWRI)) {
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182 | BIO_UNLOCK(); |
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183 | bwrite(bp); |
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184 | goto start;
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185 | } |
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186 | bp->b_flags = B_BUSY; |
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187 | bp->b_dev = dev; |
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188 | bp->b_blkno = blkno; |
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189 | } |
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190 | mutex_lock(&bp->b_lock); |
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191 | BIO_UNLOCK(); |
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192 | DPRINTF(VFSDB_BIO, ("getblk: done bp=%x\n", bp));
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193 | return bp;
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194 | } |
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195 | |||
196 | /*
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197 | * Release a buffer, with no I/O implied.
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198 | */
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199 | void
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200 | brelse(struct buf *bp)
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201 | { |
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202 | ASSERT(ISSET(bp->b_flags, B_BUSY)); |
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203 | DPRINTF(VFSDB_BIO, ("brelse: bp=%x dev=%x blkno=%d\n",
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204 | bp, bp->b_dev, bp->b_blkno)); |
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205 | |||
206 | BIO_LOCK(); |
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207 | CLR(bp->b_flags, B_BUSY); |
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208 | mutex_unlock(&bp->b_lock); |
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209 | if (ISSET(bp->b_flags, B_INVAL))
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210 | bio_insert_head(bp); |
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211 | else
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212 | bio_insert_tail(bp); |
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213 | BIO_UNLOCK(); |
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214 | } |
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215 | |||
216 | /*
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217 | * Block read with cache.
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218 | * @dev: device id to read from.
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219 | * @blkno: block number.
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220 | * @buf: buffer pointer to be returned.
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221 | *
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222 | * An actual read operation is done only when the cached
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223 | * buffer is dirty.
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224 | */
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225 | int
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226 | bread(dev_t dev, int blkno, struct buf **bpp) |
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227 | { |
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228 | struct buf *bp;
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229 | size_t size; |
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230 | int error;
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231 | |||
232 | DPRINTF(VFSDB_BIO, ("bread: dev=%x blkno=%d\n", dev, blkno));
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233 | bp = getblk(dev, blkno); |
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234 | |||
235 | if (!ISSET(bp->b_flags, (B_DONE | B_DELWRI))) {
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236 | size = BSIZE; |
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237 | error = device_read((device_t)dev, bp->b_data, &size, blkno); |
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238 | if (error) {
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239 | DPRINTF(VFSDB_BIO, ("bread: i/o error\n"));
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240 | brelse(bp); |
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241 | return error;
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242 | } |
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243 | } |
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244 | CLR(bp->b_flags, B_INVAL); |
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245 | SET(bp->b_flags, (B_READ | B_DONE)); |
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246 | DPRINTF(VFSDB_BIO, ("bread: done bp=%x\n\n", bp));
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247 | *bpp = bp; |
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248 | return 0; |
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249 | } |
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250 | |||
251 | /*
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252 | * Block write with cache.
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253 | * @buf: buffer to write.
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254 | *
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255 | * The data is copied to the buffer.
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256 | * Then release the buffer.
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257 | */
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258 | int
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259 | bwrite(struct buf *bp)
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260 | { |
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261 | size_t size; |
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262 | int error;
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263 | |||
264 | ASSERT(ISSET(bp->b_flags, B_BUSY)); |
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265 | DPRINTF(VFSDB_BIO, ("bwrite: dev=%x blkno=%d\n", bp->b_dev,
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266 | bp->b_blkno)); |
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267 | |||
268 | BIO_LOCK(); |
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269 | CLR(bp->b_flags, (B_READ | B_DONE | B_DELWRI)); |
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270 | BIO_UNLOCK(); |
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271 | |||
272 | size = BSIZE; |
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273 | error = device_write((device_t)bp->b_dev, bp->b_data, &size, |
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274 | bp->b_blkno); |
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275 | if (error)
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276 | return error;
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277 | BIO_LOCK(); |
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278 | SET(bp->b_flags, B_DONE); |
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279 | BIO_UNLOCK(); |
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280 | brelse(bp); |
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281 | return 0; |
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282 | } |
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283 | |||
284 | /*
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285 | * Delayed write.
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286 | *
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287 | * The buffer is marked dirty, but an actual I/O is not
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288 | * performed. This routine should be used when the buffer
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289 | * is expected to be modified again soon.
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290 | */
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291 | void
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292 | bdwrite(struct buf *bp)
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293 | { |
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294 | |||
295 | BIO_LOCK(); |
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296 | SET(bp->b_flags, B_DELWRI); |
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297 | CLR(bp->b_flags, B_DONE); |
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298 | BIO_UNLOCK(); |
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299 | brelse(bp); |
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300 | } |
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301 | |||
302 | /*
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303 | * Flush write-behind block
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304 | */
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305 | void
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306 | bflush(struct buf *bp)
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307 | { |
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308 | |||
309 | BIO_LOCK(); |
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310 | if (ISSET(bp->b_flags, B_DELWRI))
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311 | bwrite(bp); |
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312 | BIO_UNLOCK(); |
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313 | } |
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314 | |||
315 | /*
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316 | * Invalidate buffer for specified device.
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317 | * This is called when unmount.
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318 | */
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319 | void
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320 | binval(dev_t dev) |
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321 | { |
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322 | struct buf *bp;
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323 | int i;
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324 | |||
325 | BIO_LOCK(); |
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326 | for (i = 0; i < NBUFS; i++) { |
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327 | bp = &buf_table[i]; |
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328 | if (bp->b_dev == dev) {
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329 | if (ISSET(bp->b_flags, B_DELWRI))
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330 | bwrite(bp); |
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331 | else if (ISSET(bp->b_flags, B_BUSY)) |
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332 | brelse(bp); |
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333 | bp->b_flags = B_INVAL; |
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334 | } |
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335 | } |
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336 | BIO_UNLOCK(); |
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337 | } |
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338 | |||
339 | /*
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340 | * Invalidate all buffers.
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341 | * This is called when unmount.
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342 | */
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343 | void
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344 | bio_sync(void)
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345 | { |
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346 | struct buf *bp;
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347 | int i;
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348 | |||
349 | start:
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350 | BIO_LOCK(); |
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351 | for (i = 0; i < NBUFS; i++) { |
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352 | bp = &buf_table[i]; |
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353 | if (ISSET(bp->b_flags, B_BUSY)) {
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354 | BIO_UNLOCK(); |
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355 | mutex_lock(&bp->b_lock); |
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356 | mutex_unlock(&bp->b_lock); |
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357 | goto start;
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358 | } |
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359 | if (ISSET(bp->b_flags, B_DELWRI))
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360 | bwrite(bp); |
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361 | } |
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362 | BIO_UNLOCK(); |
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363 | } |
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364 | |||
365 | /*
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366 | * Initialize the buffer I/O system.
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367 | */
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368 | void
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369 | bio_init(void)
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370 | { |
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371 | struct buf *bp;
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372 | int i;
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373 | |||
374 | for (i = 0; i < NBUFS; i++) { |
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375 | bp = &buf_table[i]; |
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376 | bp->b_flags = B_INVAL; |
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377 | bp->b_data = buffers[i]; |
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378 | mutex_init(&bp->b_lock); |
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379 | list_insert(&free_list, &bp->b_link); |
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380 | } |
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381 | sem_init(&free_sem, NBUFS); |
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382 | |||
383 | DPRINTF(VFSDB_BIO, ("bio: Buffer cache size %dK bytes\n",
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384 | BSIZE * NBUFS / 1024));
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385 | } |